LG 42LF561V No Video after backlight repair

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  • london-freddie
    Badcaps Veteran
    • May 2015
    • 472
    • UK
    #1

    LG 42LF561V No Video after backlight repair

    Hi need help again please, been working on this LG for several hours now and now stumped
    Got the tv with a backlight/ brightness fault
    Tv worked however the picture was very very dark barely watchable, could see a couple of very much darker patches as if led's had failed
    Stripped the screen and found two failed led's one very badly burnt, both short
    Replaced the two faulty led's and the backlights now seem to be ok with what now looks like full brightness
    Rebuilt the tv and hey presto no Picture now
    Been over and over all connections ie lvds
    What have I done ?????
    When powering on the tv backlights come on lighting up the screen but NO Picture
    Help Please will post some pictures in a few minutes as soon as I get them downloaded
    Tags: None
    • bman4
      Badcaps Veteran
      • Jul 2015
      • 210
      • canada
      #2
      Re: LG 42LF561V No Video after backlight repair

      I had the same problem with sharp 50. I was shure i riped the tabs but i just made sure to reseat the tcon cables and it came back. It was same style plug and it.looked pluged in and just pressed alittler harder. Hope its as easy as this or a surge killed a board. This. Is a set with a seprat tcon so Test the fuse on tcon. the xd chips like to fail on the aio main tcons but idk about that one. I see it has no heatsink.
      Last edited by bman4; 11-14-2018, 03:26 PM.

        Comment

        • london-freddie
          Badcaps Veteran
          • May 2015
          • 472
          • UK
          #3
          Re: LG 42LF561V No Video after backlight repair

          Pics of boards
          Attached Files

            Comment

            • london-freddie
              Badcaps Veteran
              • May 2015
              • 472
              • UK
              #4
              Re: LG 42LF561V No Video after backlight repair

              Tcon fuse is ok

                Comment

                • london-freddie
                  Badcaps Veteran
                  • May 2015
                  • 472
                  • UK
                  #5
                  Re: LG 42LF561V No Video after backlight repair

                  removing left and right connections one at a time from tcon to lcd makes no difference, still no video

                    Comment

                    • bman4
                      Badcaps Veteran
                      • Jul 2015
                      • 210
                      • canada
                      #6
                      Re: LG 42LF561V No Video after backlight repair

                      Do u got.12v

                        Comment

                        • london-freddie
                          Badcaps Veteran
                          • May 2015
                          • 472
                          • UK
                          #7
                          Re: LG 42LF561V No Video after backlight repair

                          Got 13.3v at tcon fuse

                            Comment

                            • london-freddie
                              Badcaps Veteran
                              • May 2015
                              • 472
                              • UK
                              #8
                              Re: LG 42LF561V No Video after backlight repair

                              Looks like I have 270v at + to backlight

                                Comment

                                • bman4
                                  Badcaps Veteran
                                  • Jul 2015
                                  • 210
                                  • canada
                                  #9
                                  Re: LG 42LF561V No Video after backlight repair

                                  Try only one side of the tcon to panel at a time and see if you get a.white screen.

                                    Comment

                                    • london-freddie
                                      Badcaps Veteran
                                      • May 2015
                                      • 472
                                      • UK
                                      #10
                                      Re: LG 42LF561V No Video after backlight repair

                                      Yes did only try removing tcon to panel ribbons one side at a time, neither ribbon disconnected made any difference to screen, no white screen on either side

                                        Comment

                                        • vinceroger69
                                          Badcaps Legend
                                          • Mar 2012
                                          • 6714
                                          • uk
                                          #11
                                          Re: LG 42LF561V No Video after backlight repair

                                          on the tcon the two ribbon cables going to the lcd panel pcb, have you re seated them in that end under the black plastic.

                                            Comment

                                            • london-freddie
                                              Badcaps Veteran
                                              • May 2015
                                              • 472
                                              • UK
                                              #12
                                              Re: LG 42LF561V No Video after backlight repair

                                              Yes sure I have reseated them well but will recheck again now

                                                Comment

                                                • london-freddie
                                                  Badcaps Veteran
                                                  • May 2015
                                                  • 472
                                                  • UK
                                                  #13
                                                  Re: LG 42LF561V No Video after backlight repair

                                                  just reseated both ribbons no change still no video

                                                    Comment

                                                    • budm
                                                      Badcaps Legend
                                                      • Feb 2010
                                                      • 40746
                                                      • USA
                                                      #14
                                                      Re: LG 42LF561V No Video after backlight repair

                                                      https://www.badcaps.net/forum/attach...9&d=1542229704
                                                      T-CON board has Voltage test points that I can see some of them in your pictures:
                                                      Vin, HVDD, VGH, VGL, VCC, VCOM, etc. you should test them to see what they have.
                                                      Never stop learning
                                                      Basic LCD TV and Monitor troubleshooting guides.
                                                      http://www.badcaps.net/forum/showthr...956#post305956

                                                      Voltage Regulator (LDO) testing:
                                                      http://www.badcaps.net/forum/showthr...999#post300999

                                                      Inverter testing using old CFL:
                                                      http://www.badcaps.net/forum/showthr...er+testing+cfl

                                                      Tear down pictures : Hit the ">" Show Albums and stories" on the left side
                                                      http://s807.photobucket.com/user/budm/library/

                                                      TV Factory reset codes listing:
                                                      http://www.badcaps.net/forum/showthread.php?t=24809

                                                        Comment

                                                        • london-freddie
                                                          Badcaps Veteran
                                                          • May 2015
                                                          • 472
                                                          • UK
                                                          #15
                                                          Re: LG 42LF561V No Video after backlight repair

                                                          Hi again budm, as suggested I just checked tcon board voltage test points 12 in all including vcom, vst etc. No test points showed any readings, every test point showing 0V

                                                            Comment

                                                            • london-freddie
                                                              Badcaps Veteran
                                                              • May 2015
                                                              • 472
                                                              • UK
                                                              #16
                                                              Re: LG 42LF561V No Video after backlight repair

                                                              Hi just tried same test on tcon test points with both ribbons removed between tcon and panel, still no voltages measured at any of the test points, only seem to have 13.3 at the tcon fuse
                                                              all power board voltages appear ok

                                                                Comment

                                                                • london-freddie
                                                                  Badcaps Veteran
                                                                  • May 2015
                                                                  • 472
                                                                  • UK
                                                                  #17
                                                                  Re: LG 42LF561V No Video after backlight repair

                                                                  I am thinking I have a failed tcon or mainboard, unless anyone has any other ideas, but I am only guessing now

                                                                    Comment

                                                                    • Andrew F. Ali
                                                                      Badcaps Legend
                                                                      • Jan 2014
                                                                      • 2450
                                                                      • Trinidad & Tobago
                                                                      #18
                                                                      Re: LG 42LF561V No Video after backlight repair

                                                                      Is that 13.3 Vdc on both sides of the T-CON fuse? Are the Panel edge Bds. free and not touching any metal parts of the chassis? Are the cables to and from the T-CON inserted correctly and not upside down, especially the LVDS cable?

                                                                        Comment

                                                                        • london-freddie
                                                                          Badcaps Veteran
                                                                          • May 2015
                                                                          • 472
                                                                          • UK
                                                                          #19
                                                                          Re: LG 42LF561V No Video after backlight repair

                                                                          yes 13.3v at either end of tcon fuse, panel edge boards not touching any frame parts, cables fitted correctly

                                                                            Comment

                                                                            • vinceroger69
                                                                              Badcaps Legend
                                                                              • Mar 2012
                                                                              • 6714
                                                                              • uk
                                                                              #20
                                                                              Re: LG 42LF561V No Video after backlight repair

                                                                              have you got a scope to test the lvds signal wires usually pairs i think if you press the remote whilst testing in sure you should see some signal on the wires maybe budm etc can advise more on this test

                                                                                Comment

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